Connecter-switch circuits



Feb. 18, 1930. HQVLAND 1,747,169

. CONNECTER SWITCH CIRCUITS Filed Aug. 18, 1927 //vv/v r0R' HENRY 470VLAND 5y imam ATTORNEY Patented Feb. 18, 1930 UNITED STATES PATENToFFIcE HENRY HOVLAND, OF HUNTINGTON, vN'Jilfil' YORK, ASSIGNOR TO BELLTELEPHONE LAB- ORATORIES, INCORPORATED, OF NEW YORK, N. Y., ACORPGRATION OF NEW YORK CONNECTER-SWI'ICH CIRCUITS Application filedAugust 18, 1927.

This invention relates to telephone exchange systems employing automaticswitches and has for its object the provision of an improved arrangementfor selecting one of a plurality of lines serving a private branchexchange.

In accordance with the present invention, the lines leading to a privatebranch exchange are arranged in groups and means is provided for markingthe group which is first to be tested by a particular selector switchfor the purpose of finding an idle trunk. It all of the trunks of thegroup prove to be busy, the selector is restored to normal and is thenmade to select another group and to test the trunks in that group. Theinvention is applied to a switch of the t'wo motion type such as isemployed in step-by-step dial switching systems. An auxiliary switch orregister is provided which responds to dial impulses to mark a level ofthe main switch. The main switch is then operated to select the markedlevel and is then rotated to test for an idle trunk in the level. it alltrunks of the level are busy, the switch is restored to normal, and theauxiliary switch is advanced one step to mark another level which themain switch will then select and test. According to this arrangement, anumber of groups of trunks may be assigned to serve a particular branchexchange. The cross connections to the auxiliary switch permit theditlerent main switches to hunt over the levels in different orders sothat the wear on the switches and the time necessary to find an idletrunk is reduced.

To enable the main switch to be more quickly arrested upon testing atrunk and finding it idle, a ditterentially wound test relay is providedwhich also serves as a stepping relay to control both the vertical androtary step-ping movements of the main switch. This Serial No. 213,760.

to be released by the called subscriber if the calling subscriberrestores his receiver to the switchhook first, by momentarilywithdrawing the holding ground from the sleeve conductor extending fromthe connecter switch back to the preceding selector. In order that thisholding ground shall be withdrawn for an interval only sufficient toinitiate the release of preceding switches, and shall be again appliedto prevent the connecter from again being seized by another selector, arelay is provided Whose energizing and releasing characteristics arecontrolled by a resistance connected in series therewith. Provision isalso made for reducing the hunting time of the connecter over largetrunk groups comprising several bank levels, by extending the teppingcircuit of the vertical magnet over a back contact of the releasemagnet, so that immediately upon the release of the connecter thevertical magnet is operative to again advancethe connecter in itsvertical level hunting movement. The brushes of the connecter arearrested in their hunting movement over a bank level, on the last'set tterminals in the level rather than after they have rotated beyond thelast set of terminals, and are then restored to normal. This overcomesthe tendency ot' the brushes to snag on the last terminal set as theyreenter the bank in their restoring movement.

The invention. will be more clearly understood from a consideration ofthe following description taken in connection with the attached drawingin which the single figure shows a connecter switch embodying theinvention.

The connecter switch indicated by brushes 101, 102 and 103 is of thetype usually employed in step-by-step dial systems and has two mot-ions,a vertical motion to select levels of bank terminals, and a rotarymotion to select a terminal in a level. No attempt has been made to showthe terminal bank since it is of well known construction. The connecterhas, in addition to the usual brushes 101, 102 and 108, an auxiliarybrush 104 which makes contact with a segment of commutator 105 at eachlevel to which the brush setis raised. The auxiliary switch comprisingbrushes 106 and 107 is a rotary switch having a definite normalposition.

If the subscriber at substation 100 wishes to be connected with asubscriber whose substation, such as 110, is located in a private branchexchange, he will remove the receiver from the switchhook and willoperate his dial to transmit impulses corresponding to the number of theprivate branch exchange. The dialing of the earlier digits of the numberwill bring about the establishment in the well known manner of aconnection to the terminals 111, 112 and 113 extending to a connecterswitch especially adapted for completing connections to branchexchanges. The switches 108 and 109 indicate the necessary train ofswitches for extending the connection to this point.

As soon as switch 109 comes to rest, a circuit is completed from batterythrough the upper winding of relay 114, upper normal contact of relay115, terminal 112 over the ring conductor extending through the train ofswitches, through subscribers substation 100, back over the tipconductor through the train of switches to terminal 111, lower normalcontact of relay 115, lower winding of relay 114 to ground. Relay 114operates, in turn operating relay 117. Relay 117 connects ground overits innermost upper front contact to terminal 113 to hold the train ofswitches.

\Vhen the subscriber now dials the next to the last digit of the wantednumber, relay 114 releases at each interruption of its circuit. Relay117 is slow to release and maintains its armatures attracted throughoutdialing. Each release of relay 114 closes a circuit from ground over theback contact of relay 114, lower front contact of relay 117, jumperconnection 155, innermost lower back contact of relay 122, winding ofrotary magnet 119 of the auxiliary switch to battery. A circuit is alsoclosed in parallel with the winding of magnet 119 which extends over theinnermost upper back contact of relay 122 to the winding of relay 120and battery. At the first impulse, relay 120 operates, opening a circuitto brush 107 which will be traced hereinafter, and being slow to releaseholds this circuit open until the digit has been completely dialed.Magnet 119 advances the auxiliary switch one step for each impulse.Assuming that the digit dialed is 3, brush 107 will come to rest on itsthird terminal.

Relay 120 releases following the last impulse of the digit, and closes acircuit from battery, through the winding of relay 122, off-normalcontact 121 of the auxiliary switch, left back contact of relay 120,inner upper contact of relay 117 to ground. Relay 122 operates and locksover off-normal contact 121, the upper contact of relay 117 to ground atthe lower front contact of relay 122.

The operation of relay 122 prevents the dialing of a further digit fromaffecting the auxiliary switch. The rotary off-normal contacts 148 alsoclose at this time to prepare a circuit for the release magnet 147 ofthe auxiliary switch.

A circuit is now closed for relay 127, from battery through the windingof relay 127, outer back contact of rotary magnet 126, back contact ofvertical magnet 125, inner upper back contact of relay 128, normallyclosed vertical off-normal contacts 154, right back contact of relay120, back contact of connector release magnet 134, lowermost backcontact of relay 123, off-normal contact 121, left back contact of relay120 to ground at the inner upper front contact of relay 117. Relay 127operates in this circuit, closing a circuit from battery through thewinding of vertical magnet 125, innermost lower back contact of relay128, upper front contact of relay 127, normally closed tenth rotary stepsprings 124 to ground at relay 117, as previously traced. Magnet 125operates to elevate the connecter brush set one step and to open thecircuit of relay 127. Relay 127 opens the circuit of magnet 125. lVhenmagnet 125 releases, relay 127 is reoperated after which magnet 125reoperates and takes another Vertical'step.

Following the third vertical step, brush 104 will make contact with thethird segment of commutator 105 and a circuit will be completed fromground at the intermediate front contact of relay 117, left back contactof re lay 120, off-normal contacts 121, lower back contact of relay 123,back contact of magnet 134, right back contact of relay 120, loweralternate off-normal contact 154, now closed, brush 107 and its thirdterminal, the third segment of commutator 105, brush 104, lower windingof relay 128, the outer back contact of rotary magnet 126, lower windingof relay 127 to battery.

Relay 127 is held operated. Relay 128 operates in this circuit and locksover its inner upper front contact, off-normal contacts 154, backcontact of relay 120 to ground as previously traced. Relay 128is slow tooperate in order to delay the first rotary step until the brushes havecome to rest after the vertical movement. The operation of relay 128transfers the circuit closed by relay 127 from the vertical magnet 125to the rotary magnet 126. hen relay 128 completely operates, magnet 126operates, opening the circuit of relay 127. Magnet 126 and relay 127operate and release in the manner previously described in connectionwith the operation of magnet 125. Each time that relay 127 releasesfollowing a rotary step, a circuit is prepared from ground at the lowerfront contact of relay 122, inner lower back contact and lower windingof relay 123, upper winding and upper normal contact of relay 127 tosleeve brush 103. Busy trunks are characterized by ground connected totheir terminals and idle trunks by battery.

Assuming that none of the trunks in the third level are idle, the abovetraced circuit will not be completed and the connecter switch will taketen steps testing each terminal in the level. At the tenth rotary stepof the connecter, the tenth rotary step springs will be operated.Springs 12 1 are now opened to prevent the further operation of therotary magnet 126. A circuit is also closed from ground at the lowerfront contact of relay 122, over the upper front contact of relay 117,inner back contact of rotary magnet 126, inner lower front contact ofrelay 127, contact 132, brush 106 and its third terminal, verticaloff-normal contact 133, the winding of connecter release magnet 131- andbattery. Release magnet 134: closes a circuit for itself over contact133 to ground at its left front contact to insure its continuedenergization until the switch reaches its normal position. lVith releasemagnet 134 operated, ground is removed from brush 107 and the circuit ofrelay 127 is held open. Upon the energization of magnet 134, a circuitis closed from battery through the winding of rotary magnet 119 of theauxiliary switch, front contact of release magnet 134, lower backcontact of relay 123, off-normal contacts 121, left back contact ofrelay 120 to ground at the intermediate front contact of relay 117.Magnet 119 operates in this circuit, advancing the auxiliary switch onestep and releases when the release magnet 13 1 releases. When therelease magnet 134 retracts its armatures, the circuit of relay 127 isimmediately reclosed and the vertical magnet is operated to elevate theconnecter brush shaft to the level marked by the next terminal of theauxiliary switch. This need not be the next level of the switch but maybe as shown the seventh level or any other level included in the "groupserving the particular branch exchange. In the connecter switches havingaccess to these trunks, the marking of the trunks will usually bearranged in various orders so that the orders of testingthe levels willdiffer between switches.

It will be noted that the rotary step springs 132 closed when thebrushes 101-, 102, and

'103 were resting on the tenth or last terminal set of the third banklevel and that the switch shaft was restored to normal from thisposition. Since the brushes have therefore not been stepped-off of thelast terminal set of the level there is no tendency for them to snag ontheir restoring movement as would be the case were the springs 132closed in the eleventh rotary step position of the switch shaft when thebrushes would bein a position beyond the last terminal set of the banklevel.

Assuming that a trunk in level 7 is idle, battery connected to brush 103over that trunk will complete'the circuit above traced through windingsof relays 123 and 127, operating relay 123 and releasing relay 127 sincethe current now flowing in its upper winding sets up a fiuX inopposition to the flux created by current flowing through the lowerwinding. Relay 123 locks in a circuit from battery through its upperwinding, and upper front contact, innermost lower back contact of relay127, inner back contact of magnet 126, upper front contact of relay 117to ground at the front contact of relay 122. Ihe operation of relay 123disconnects ground from brush 107 and also from the locking circuit ofrelay 128 and the circuit through the lower winding of relay 127. Italso opens the circuit through the upper winding of relay 127 so thatrelay 127 is not permitted to reoperate. In addition, it closes acircuit from ground over the intermediate lower front contact of relay122, inner lower front contact of relay 123 to brush 103 to hold thecalled trunk busy. It may be noted at this time that relay 123 issuiiiciently marginal not to operate when two switches test a trunksimul taneously.

Relay 123, in operating, connects ringing current from source over itsuppermost front contact, upper winding of relay 136, up-

per back contact of relay 136, upper back contact of relay 128,intermediate upper front contact of relay 123, brush 102 to the privatebranch exchange and back over brush 101, lower front contact of relay123, lower back contact of relay 128,innermost lower back contact ofrelay 136 to ground. transmitted to the calling subscriber throughcondensers 139 and 140. The ringing current signals the branch exchange,which answers, completing a direct current circuit in the well knownmanner. to the ringing current but does operate in the direct currentcircuit closed at the branch exchange. Resistance 137 and condenser 138are supplied to protect the upper contact of relay 136. Relay 136 looksin a'circuit from battery through its lower winding and inner lowerfront contact to ground at the front contact of relay 122. When relay136 operates, it connects the talking conductors from terminal 111,condenser 141, middle lower .2

front contact of relay 136, lower back contact of relay 128, lower frontcontact of relay 123 to brush 101, and also from terminal 112, condenser140, uppermost front contact of relay 136, uppermost back contact ofrelay 128, intermediate upper front contact of relay 123 to brush 102.Talking current is sup frontcontact of relay 123, upper back contact:

A ringing tone is Relay 136 is not responsive. a:

of relay 128, upper front contact of relay 136, upper winding of relay115 to ground. Relay 115 operates in this circuit, connecting groundover the back contact of relay 120 to terminal 113. It also reverses theconnection of the windings of relay 114 to the incoming tip and ringconductors for supervisory purposes.

Vhen the calling subscriber restores his receiver to the switchhook,relay 114 is released, in turn releasing relay 117. The release of relay117 opens the ground connection from its front contact to terminal 113.Since relay 117 is slow to release, a circuit will be closed for a shortinterval from ground over the back contact of relay 114, front contactof relay 117, through resistance 150, lowermost front contact of relay136, which is held operated under the control of the called subscriber,to the winding of relay 120 and battery. Relay 120 energizes but as itscircuit includes resistance 150 its core does not become fully saturatedso that when its circuit is opened upon the release of relay 117, it isnot as slow in releasing as it normally is. Relay 120 does not releasetherefore for a short interval following the release of relay 117 andground from the front contact of relay 115 is thereby removed fromterminal 113 to permit the release of the train of switches used inbuilding up the connection to the connecter. As soon as relay 120releases, ground is again connected to terminal 113 from relay 115 toprevent the re-selection of the connecter before the called subscriberrestores his receiver. Ground from the inner upper front contact ofrelay 115 holds relays 122, 123 and 136 operated under the control ofthe called subscriber.

If the called subscriber is the first to hang up, relay 115 releases butrelays 122, 123 and 136 are held operated under the control of relay 117and the restoration of the receiver by the calling subscriber completelyreleases the connecter. lVhen both relays 117 and 115 have beenreleased, relays 122, 123 and 136 also release. with relays 115 and 117both released, a circuit is closed from battery through the winding ofconnecter release magnet 134, vertical off-normal contact 133, lowerback contact of relay 122, lower back contact of relay 115, backcontacts of relays 117 and 114 to ground. The operation of magnet 134restores the connecter switch to normal. A branch of this circuitextends from battery through the winding of auxiliary switch releasemagnet 147, off-normal contact 148, to the back contact of relay 115 andthence to ground. The operation of magnet 147 restores the registerswitch to normal.

For the purpose of restoring a connecter to normal when either thecalled or the calling subscriber fails to hang up within a reasonablelength of time, two supervisory circuits are provided. The circuit forsupervising the release by the calling subscriber extends from groundover the back contacts of relays 114 and 117, inner lower front contactof relay 115 to a supervisory circuit (not I battery through meter 153,vertical olf-normal contact 152 to ground at the middle lower backcontact of relay 122.

If all of the trunks in the seventh level had been busy, the connecterwould have been restored and then directed to level 6. imilarly, theother levels would have been tested in turn if no idle trunks wereavailable in any of them. According to the cross-connecting arrangementshown in drawing, level 4 is the last one to be tested with brush 107engaging its seventh terminal. The terminal of brush 106 is thereforenot connected to the circuit of release magnet 134- and the closure ofthe tenth rotary step springs does not release the connecter switch. Theclosure of contact 131 connects tone from coil 149 over the lower frontcontact of relay 127 to the ring conductor and thence through condenser140 to the subscribers substation informing him that no trunks to thebranch exchange are available. This tone circuit now remains closeduntil the calling subscriber restores his receiver and releases theconnecter. I

In order to record the number of times that all of. the trunks leadingto a particular branch exchange are busy when a call is attempted, ameter 151 may be connected to the terminal of the auxiliary switchcorrespond ing to the last group of trunks to be tested, so that uponthe closure of the tenth step springs, a circuit is completed fromthe'meter over brush 106 and the tenth rotary step spring 132, frontcontact of relay 127, inner back contact of magnet 126, back contact ofrelay 120 to groundover the middle front contact of relay 117.

It Will be apparent that if a particular branch exchange requires theservices of the entire number of trunks outgoing from a connecterswitch, the auxiliary switch must be advanced only one step in order tostart the automatic hunting operation. The modification of the circuitto render the operation of the auxiliary switch independent of thenumber of impulses of the first digit dialed into the connecter switch,may be made by opening strap 155 and closing strap 156. The circuit ofmagnet 119 of the auxiliary switch now extends over the right frontcontact of relay 120, strap 156 to ground over the uppermost backcontact of relay 122. Therefore, when relay 120 operates in response tothe first impulse dialed into the 'connecter, rotary magnet 119 isoperated and is held operated under the control of relay 120 until thedialing operation is completed. Therefore, irrespective of the digitemployed, the rotary switch will make but one step after which theautomatic operation will proceed substantially as hereinbeforedescribed.

lVhen the release magnet 134: operates after all of the trunks of alevel have been found busy, and the switch starts to restore, a circuitis closed from ground over the middle contact of relay 117, left backcontact of relay 120, ofi-normal contact 121, lower back contact ofrelay 123, right front contact of magnet 134, winding of magnet 119 tobattery. Magnet 119 thereupon operates advancing the auxiliary switchone step. When the switch is completely restored, release magnet 134 isdeenergized, opening the circuit of magnet 119. After the last level inthe group has been tested, no circuit is closed for magnet 13 1 so thatmagnet 119 is not operated and a busy tone is transmitted to the callingsubscriber as previously described.

The alteration of the connecter circuit from one serving several privatebranch exchanges to one serving only one private branch exchange maytherefore be very easily accomplished by supplying the two straps 155and 156.

What is claimed is:

1. In a telephone system, a selector switch, a magnet for advancing saidswitch in a hunting movement, a double wound test relay in said switch,a circuit for said magnet controlled by said relay, an energizingcircuit for said relay extending through one of its windings, a testbrush for said switch, and a circuit extending from said test brushthrough the second winding of said relay, the windings of said relaybeing arranged in opposition whereby when said test brush engages theterminal of an idle line the energization of said relay is prevented toarrest the further advance of said switch.

2. In a telephone system, a selector switch, a magnet for advancing saidswitch in a hunting movement, a double wound test relay, a circuit forenergizing said relay over one of its windings and under the control ofsaid magnet, a circuit for said magnet closed upon the energization ofsaid relay whereby said relay and magnet reciprocally operate to causethe advance of said switch, and a test brush for said switch connectedin circuit with the other winding of said relay, the windings of saidrelay being arranged in opposition whereby when said test brush engagesthe terminal of an idle line the energization of said relay is preventedto arrest the further advance of said switch.

3. In a telephone system, a selector switch having one motion to selecta group of lines,

and a second motionto select an idle line of a group, a magnet forcontrolling said first motion, a second magnet for controlling saidsecond motion, a double Wound test relay, a circuit for energizing saidrelay over one of its windings and under the control of either one ofsaid magnets, circuits for said magnets closed upon the energization ofsaid relay whereby said relay and magnets operate reciprocally first tocause said switch to be moved to select a group of lines, and then to be.moved to hunt for an idle line in a group, and a test brush for saidswitch connected in circuit with the other winding of said relay, thewindings of said relay being arranged in opposition whereby when saidfirst brush engages the terminal of an idle line the energization ofsaid relay is prevented to arrest the further hunting movement of saidswitch.

4. In a telephone system, a calling line, a called line, a train ofswitches for extending a connection from said calling line to saidcalled line, a line relay and first and second slow-releasing relayscontrolled by said calling subscriber to govern the setting of the lastswitch of the train, said first slow relay being operable over a frontcontact of said line relay and said second slow relay being operableover a back contact of said line re lay and a front contact of saidfirst slow relay,.a holding circuit extending from the last switch ofthe train to the preceding switches, a first ground connection for saidholding circuit controlled by said first slow relay, a second groundconnection for said holding circuit controlled over a back contact ofsaid second slow relay, a resistance for insertion in series with saidsecond slow relay to render it quicker to release, and circuitconnections whereby when said calling subscriber restores his receiverbefore said called subscriber, said line relay releases followed insuccession by the operation of said second slow relay to open saidsecond ground con= nection, by the release of said first slow relay toopen said first ground connection, thereby causing the release ofpreceding switches, and by the release of said second slow relay toagain apply said second ground connection to thereby render said lineswitch unselectable.

5. In a telephone system, a calling line, a called line, a train ofswitches for extending a connection from said-calling line to. saidcalled line, a line relay and first and second slow-releasing relayscontrolled by said calling subscriber to govern the setting of the lastswitch of the train, said first slow relay being operable over a frontcontact of said line relay and said second slow relay being operableover a back contact of said line relay and a front contact of said firstslow relay, a holding circuit extending from the last switch of thetrain to the preceding switches, a first ground connection for saidholding circuit controlled by said first slow relay, a second groundconnection for said holding circuit controlled over a back contact ofsaid second slow relay, means controlled by the response of the calledsubscriber to render said second slow relay quicl er to release, andcircuit connections whereby when said calling subscriber restores hisreceiver before said called subscriber said line relay releases followedin succession by the operation of said second slow relay to open saidsecond ground connection, by the release of said first slow relay toopen said first ground connection, thereby causing the release ofpreceding switches, and by the release of said second slow relay toagain apply said second ground connection to thereby render said lineswitch unselectable.

6. In a telephone system, a plurality of groups of lines, a selectorswitch, means for operating said switch to select one of a plurality ofsaid groups, means for then moving said switch to hunt for an idle linein said group, a magnet for restoring said switch if all the lines insaid group are busy and means controlled over a back contact of saidmagnet upon the complete release of said switch to then cause saidswitch to automatically select another of said groups and to hunt for anidle line in such other group.

7. In a telephone system, a selector switch, a group of linesterminating therein, means for advancing the brushes of said switch in ahunting movement over the terminals of said lines, and means forautomatically releasing said switch from the terminals of the last lineof the group in response to a non-selectable condition of said lastline.

8. In a telephone system, a selector switch, a group of linesterminating therein, means for advancing the brushes of said switch in ahunting movement over the terminals of said lines, shaft contacts closedwhen said brushes engage the terminals of the last line of the group,and means for releasing said switch from the terminals of the last lineupon the closure of said contacts in response to a nonselectablecondition of said last line.

9. In a telephone system, a selector switch, a group of linesterminating therein, means for advancing the brushes of said switch in ahunting movement over the terminals of said lines, means for arrestingsaid brushes on the terminals of the last line of said group. and

means for thereupon releasing said switch in response to anon-selectable condition of said last line.

10. In a telephone system, a selector switch, a group of linesterminating therein, means for advancing the brushes of said switch in ahunting movement over the terminals of said lines, means for arrestingsaid brushes on the terminals of the last line of said group, shaftcontacts closed when said brushes engage the terminals of the last lineof the group, and means for releasing said switch from the terminals ofthe last line upon the closure of said contacts if said last line is ina non-selectable condition.

11. In a telephone system, a selector switch, a group of linesterminating therein, means for advancing the brushes of said switch in ahunting movement over the terminals of said lines, means for releasingsaid switch, and shaft contacts operated when said brushes engage theterminals of the last line of the group to arrest the further advance ofsaid switch and to cause the operation of said releasing means if saidlast line is in a nonselectable condition.

In witness whereof, I hereunto subscribe my name this 12 day of AugustA. 1)., 1927.

HENRY HOVLAND.

DISCLAIMER 1,747,169.Henry Hovland, Huntington, N. Y. CoNNEcrER-SwI'roHCIRCUITS.

Patent dated February 18, 1930. Disclaimer filed July 2, 1931', by theassignee,

Bell Telephone Laboratories, Incorporated.

Hereby enters this disclaimer to the said claim of said Letters Patentwhich is in the following .words to wit:

4. In a telephone system, a calling line, a called line, a train ofswitches for extending a connection from said calling line to saidcalled line, a line relay and first and second slow releasing relayscontrolled by said calling subscriber to govern the setting of the lastswitch of the train, said first slow relay being operable over a frontcontact of said line relay and said second slow relay being operableover a back contact of said line relay and a front contact of said firstslow relay, a holding circuit extending from the last switch of thetrain to the preceding switches, a first ground connection for saidholding circuit controlled by said first slow relay, a second groundconnection for said holding circuit controlled over a back contact ofsaid second slow relay, a resistance for insertion in series with saidsecond slow relay to render it quicker to release, and circuitconnections whereby when said calling subscriber restores his receiverbefore said called subscriber, said line relay releases followed insuccession by the operation of said second slow relay to open saidsecond ground connection, by the release of said first slow relay toopen said first ground connection, thereby causing the release ofpreceding switches, and by the release of said second slow relay toagain apply said second ground connection to thereby render said lineswitch unselectable.

(Ofiic'lal Gazette July 21, 1931.)

